It is common in many industries to use containers or vessels for handling, processing, transporting or temporarily storing particulate bulk materials. The geometrical configuration of such containers or vessels is of utmost importance in order to assure the desired type of flow of particles through said vessels. Depending on such factors and characteristics of the particles, as for example, the size and shape of the particles, the friction forces developed in the body of the bulk material as well as the friction forces between the particles and the wall of the container and the pressure exerted on said particles caused by the weight of the mass of particles, primarily the shape of the vessel but also its dimensions relative to the particles to be handled, determines whether the particles will flow freely by the action of gravity or will form bridges or domes which stop said flow or at least produce non-uniform flow thereof.
U.S. Pat. No. 4,886,097 to Garza-Ondarza discloses a single segment container to handle particulate solids comprising a downwardly converging wall which wall is provided with an internal inverted step extending along a portion of the converging wall. The internal inverted step extends helically along at least a portion of the converging wall to provide a continuous increase in the cross-sectional area of the container to promote the flow of solids.
This patent provides an enlargement of the cross-sectional area of the container and in this way the solids compaction is minimized allowing configurations of the container with narrower outlet diameters. The measures proposed by this patent however, although effective in achieving its object, are difficult to incorporate in a cost-effective manner because the construction of the helical step along the conical portion of the container raises the costs incurred by the actual cutting and conformation of the metal sheet employed for constructing such container. This becomes more relevant when the spiral inverted step is to be incorporated in a large reactor which has to withstand high internal pressures.
U.S. Pat. No. 6,055,781 describes a hopper that has been developed to reduce the tendency of particulate material to form bridges by providing a shape so that its walls slope downward more steeply with increasing height above the outlet. The disclosed hopper comprises several adjacent conical sections that are arranged along a common longitudinal axis. In the downward direction, the conicity of the adjacent sections decreases.
U.S. Pat. No. 3,797,707 describes a bin for storage and flow of bulk solids having stepped hopper surfaces adapted to increase and render constant the rate of flow at the hopper outlet. The stepped surfaces have friction and slope angles adapted to satisfy the criteria for mass flow, and provide spaces for injecting fluid at one or more perimetric interfaces with the moving solids. This patent suggests an enlargement of the cross sectional area of the bin. To this end, it is propagated to arrange several conical segments adjacent one another and along a common longitudinal axis. The segments are dimensioned and arranged in the longitudinal direction so that they are joined by horizontal wall segments. The walls of this known container may still provide a support for the formation of domes by the particles. The injection of a fluid may not be possible to practice in many applications and entails additional operational costs.
U.S. Pat. No. 3,921,351 discloses a segmented storage bin of circular or square cross-section for storing and dispensing particulate material comprising several bin segments; the cross-section of the bin is enlarged by the combination of intermediate wall segments providing an enlargement of the cross sectional area of the bin. The concept described in this patent however does not eliminate the formation of domes by the solid particles.
U.S. Pat. No. 6,089,417 describes a chip bin comprising a discharge zone having a curvilinear roller shape in any freely chosen horizontal cross-section wherein the cross-section of the discharge zone decreases downwardly. In the cross-sectional view along the longitudinal axis of the known chip bin, some segments of the bin have a vertical wall on one side and an angled wall on the opposite side. The bin of this patent also has the disadvantage of a complicated and costly construction because of the shape of the segments as shown in the patent.